If the oil was changed every 3000 miles and wasnt severly abused I woundnt do anything to it. Regular oil changes keep engines running clean. If you insist cleaning your motor I would use Rislone with your next oil change. I have heard some good things.

If you are wanting to clean the inside of the engine and not do any damage, I would suggest using Auto-Rx. It is ester based, does not strip the engine, and it takes 700-1000 miles to clean the engine. This should be the link www.auto-rx.com make sure to read and follow the instructions. Any of the XX minute flushes will break down the viscosity of the oil and strip the engine which can harm seals- don't use them.

Originally posted by Dan76'F100 How about running gas or diesel fuel in the motor for 10 minutes or so, well that's what my dad would do

You've got to be crazy to do that. I've heard of one person who did that in the past, and it didn't seem like a good idea. These are FUELS, not lubricants. I would think any friction that occurs will cause some damage that greatly outweighs any cleaning benefit.

If you have maintained your engine regularly, I wouldn't worry about doing anything. Even with dino oil, engines stay very clean with the modern additive packages in the oil. I would think running a cleaner could even cause the seals to start leaking.

Originally posted by Dan76'F100 How about running gas or diesel fuel in the motor for 10 minutes or so, well that's what my dad would do
How about Marvel mystery oil, what does that do?

Actually, there are some people around here who advocate running a quart or so of diesel fuel in the motor oil for 5-10 minutes at idle just before the oil drain. If you do a search in this forum you'll find some threads on it with people going back and forth on the issue.

Also, one time I had a chance to smell the Gunk brand XX minute oil flush that you see on the shelves. I saw some guy pouring it into his engine in the parking lot of an auto parts store (don't know what he was thinking ) So I asked if I could look over the empty container and smell it. If that stuff isn't diesel fuel and/or kerosene than I need a new nose.

People also have reported good results with MMO, and then there are others who have debated its usefulness. If you do a search on Marvel you'll find some opinions on that stuff, as well.

Originally posted by gavin If you just run a good synthetic oil, for a couple of change intervals, that'll clean out most of the old carbon/coke build up. Synthetic has a much higher detergent value than dino.

Not true. Modern dino oils have quite a substantial additive package. Running a synthetic oil will not "clean out" deposits in the engine. If this was the case, it would damage your engine in the process.

Originally posted by johnsdiesel Not true. Modern dino oils have quite a substantial additive package. Running a synthetic oil will not "clean out" deposits in the engine. If this was the case, it would damage your engine in the process.

I'm not sure - not that synethetic has some sort of super harsh additive package, but I've heard from numerous places (granted, most of them were here on FTE) that many synthetics have excellent detergent properties, and this is part of the problem - not only do they flow better, but they clean away some of the buildup that can block leaks, effectively making the hole bigger. Therefore, it can leak.

I can't vouch for the legitimacy of this claim; I personally haven't seen any concrete evidence that indicates the presence of a higher detergent value, but you are the first person I've seen so far to dispute it.

Now, back to the task at hand - if your oil has been changed regularly, then you really have no need to clean it out. IMO, if it needs to be "cleaned out", then it probably hasn't been taken care of and will need to be replaced anyway. Stick to regular oil change intervals, and forget about the OTC engine flush stuff - it just thrashes your seals.

I'd be more worried about carbon build-up in the heads and pistons etc. That can be fixed with a good dose of lead foot driving. Ive seen inside some high mileage motors and I dunno if it's the greatest idea to get all that gunk flying through the bearings and so on. I take the pan off and scrape the junk out just to be on the safe side. I must say the newest motor I have is 31 years old though...

I used to put diesel fuel in my 72 GMC with a 250 - 6 cylinder. Boy the engine was clean after that. Used 4 quarts of diesel fuel for about a half minute. Did this twice or three times. When the new oil was put in, you couldn't see it on the dip stick. Now sure about long term effects.

I have always heard 1/2 qt of trans fluid in the oil each change will keep everything clean. Actually I believe it's Toyota that used to require it because the oil channels were so thin they would block otherwise.

Best way to clean the inside of an engine is to tear it down. But my recommendation is to run a quart of rislone in it all the time. It works slow. The fast cleaners could clean so much off as to gunk up and clog small oil passages.

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